Selective Dorsal Rhizotomy in Ambulant Children with Cerebral Palsy

Current Concepts Review Selective dorsal rhizotomy in ambulant children with cerebral palsy K. K. Wang1,2 Introduction 1,3 M. E. Munger Primary neurological factors (e.g. spasticity, weakness, 1,4 B. P.-J. Chen balance, poor selective motor control) and secondary T. F. Novacheck 1,4 deformities (e.g. joint contractures, bony deformities, joint dysplasia) both compromise gait and motor function in children with cerebral palsy (CP). Correction of second- Abstract ary deformities can be done via orthopaedic interven- Background Selective dorsal rhizotomy (SDR) is a surgical tion, often in the form of single event multi-level surgery procedure for treating spasticity in ambulant children with (SEMLS).1 However, this does not address the primary cerebral palsy (CP). However, controversies remain regarding neurological factors. A growing body of literature sug- indications, techniques and outcomes. gests that selective dorsal rhizotomy (SDR) is effective in Current evidence summary Because SDR is an irreversible improving one neurological factor – spasticity, which may procedure, careful patient selection, a multi-disciplinary ap- lead to improvements in function and gait. proach in assessment and management and division of the Spasticity is defined by increased resistance with increas- appropriate proportion of dorsal rootlets are felt to be par- ing velocity of movement and/or the presence of a spas- 2 amount for maximizing safety. Reliable evidence exists that tic catch. A number of interventions are available for the SDR consistently reduces spasticity, in a predictable manner management of spasticity. Broadly, these can be described and to a substantial degree. However, functional improve- as surgical versus non-surgical, temporary versus perma- 3 ments are small in the short-term with long-term benefits nent and focal versus generalized (Fig. 1). SDR is a form of difficult to assess. surgical, permanent and relatively generalized treatment option for lower extremity spasticity that reduces tone by Future outlook There is a need for high-quality studies uti- selective sectioning of lumbosacral afferent nerve rootlets. lizing long-term functional outcomes and well-matched However, much controversy remains regarding the use control groups. Collaborative, multicentre efforts are of SDR, how patients should be selected for the procedure required to further define the role of SDR as part of the and what outcomes can be achieved.4-6 Quality long-term management paradigm in maximizing physical function in data are lacking, and much of what is done in clinical prac- spastic CP. tice is not supported by strong evidence. In addition, nat- 7 Cite this article: Wang KK, Munger ME, Chen BP-J, Novacheck TF. ural history studies exist that show reduction in spasticity 8 Selective dorsal rhizotomy in ambulant children with cerebral and improvement in gross motor function can occur in palsy. J Child Orthop 2018;12:413-427. DOI: 10.1302/1863- the absence of intervention, making results of SDR diffi- 2548.12.180123 cult to interpret without well-matched control groups. This article aims to serve two purposes: 1) to explore the Keywords: cerebral palsy; selective dorsal rhizotomy; boundaries of our knowledge by providing a review of the spasticity; interdisciplinary care current literature; and 2) to share three decades of expe- rience from our institution on the use of SDR in helping children with CP. 1Center for Gait and Motion Analysis, Gillette Children’s Specialty Healthcare, Twin Cities, Minnesota, USA The focus of this review will be on the role of SDR in 2Department of Orthopedic Surgery, Royal Children’s Hospital, maximizing mobility and independence for ambulant Melbourne, Victoria, Australia children with CP, functioning at Gross Motor Function 3 Department of Orthopedic Surgery and Department of Health Classification System (GMFCS)9 levels I to III. A nonselec- Policy and Management, University of Minnesota, Twin Cities, tive dorsal-ventral rhizotomy may be performed in indi- Minnesota, USA 4Department of Orthopedic Surgery, University of Minnesota, viduals with more severe impairments, functioning at Twin Cities, Minnesota, USA GMFCS levels IV or V, in order to meet palliative care goals such as pain relief and improvement of caregiving.10 Since Correspondence should be sent to T. F. Novacheck, Center for this is a different procedure with different indications and Gait and Motion Analysis, Gillette Children’s Specialty Healthcare, 200 University Ave E, St Paul, MN 55101, United States. expectations, it is outside the scope of this review and will E-mail: [email protected] not be addressed here. CURRENT CONCEPTS REVIEW: SELECTIVE DORSAL RHIZOTOMY Fig. 1 Tone management options in cerebral palsy. Tone management is only one aspect of the musculoskeletal care needs of children with spastic cerebral palsy: lever arm dysfunction and joint deformity are other important aspects and are not represented in this diagram. Within the tone management paradigm, options include non-invasive (green), injections (yellow) and surgical (red). Selective dorsal rhizotomy (SDR) is a form of surgical, irreversible and largely generalized option for tone reduction. Orthopaedic procedures for tone reduction include muscle/tendon lengthening and transfers (BoNT, botulinum toxin; ITB, intrathecal baclofen; DBS, deep brain stimulation; SDR, selective dorsal rhizotomy). History and rationale In recent years, some surgeons have adopted a more lim- ited laminectomy at the level of the conus as advocated In preterm infants, the deep periventricular white matter by Park and Johnston.16 Although technically more chal- is metabolically susceptible to injury. Damage to this area lenging for identification of rootlet levels, proponents of typically leads to reduced inhibitory input into the spinal the conus approach argue that it results in a smaller scar, interneuron pool from descending neural pathways. This reduced iatrogenic spinal instability, decreased postoper- results in excessive spinal cord alpha motor neuron activ- ative pain and quicker recovery.17 ity and spasticity. Afferent dorsal root input into the spinal Following his relocation to the United States from South interneuron pool has a further net excitatory effect on the Africa, Peacock helped popularize SDR in North America for on the alpha motor neurons. Dorsal rhizotomy reduces the treatment of children with spastic CP.18,19 Understand- the amount of excitation of alpha motor neurons and ing that children with spastic CP are heterogenous, Peacock thereby reduces spasticity (Fig. 2).11 helped establish a set of selection criteria for SDR to maxi- Although the first dorsal rhizotomy was performed mize safety and efficacy. These criteria were adopted by the more than 100 year ago,12 the procedure’s evolution multidisciplinary team of orthopaedic surgeons, physiatrists since then has taken several major turns. Foerster’s initial and neurosurgeons at our institution in the 1980s. In the method of non-selective rhizotomy fell into disuse for more three decades since, our protocol for the care of children in than five decades because of the adverse consequences of the SDR pathway has stayed relatively constant. The original excessive de-afferention. In the 1960s, the procedure was criteria were incorporated with pre- and postoperative 3D revised by sectioning only a fraction of the rootlets based gait analysis (3DGA), a multi-disciplinary team approach, as on the patient’s preoperative function,13 and then further well as intensive postoperative inpatient rehabilitation. refined into selective dorsal rhizotomy by electrically stim- ulating the rootlets intraoperatively and measuring the 14 electromyographic response before sectioning. In South Patient selection for SDR Africa, Peacock shifted the site of rhizotomy from the conus medullaris region to the cauda equina.15 This makes root- Although similarities exist between patient selection cri- let identification easier in an effort to avoid bladder dys- teria of various institutions, there is no consensus. Several function, one of the complications noted by Fasano et al.14 factors contribute to the lack of uniformity. Firstly, there 414 J Child Orthop 2018;12:413-427 CURRENT CONCEPTS REVIEW: SELECTIVE DORSAL RHIZOTOMY Fig. 2 Spasticity reflex arc schematic diagram. Muscle stretch stimulates dorsal (afferent) sensory nerve rootlets, which in turn has a net excitatory effect on alpha motor neurons within the spinal cord. The spasticity arc is completed via the hyperstimulated efferent ventral motor rootlets. During SDR, individual dorsal rootlets are isolated and stimulated with a Peacock probe. Those that produce inappropriate activation are sectioned. Illustration used with permission, courtesy of Timothy T. Trost. Table 1 Selection criteria for selective dorsal rhizotomy (SDR). These characteristics constitute the ‘ideal’ candidate for SDR. The perfect patient that fits all preoperative categories is rare and so discretion is necessary based on an individual’s overall picture Features ‘ideal’ for SDR Notes History Age: 4 to 10 years See discussion Birth events: hypoxic ischemic encephalopathy More likely associated with periventricular leukomalacia Birth events: prematurity < 36 weeks gestation Spastic diplegia More likely to benefit than quadriplegia (Kim 2006)66 Absence of other causes of spasticity E.g. hereditary spastic paraplegia Examination Functional level: GMFCS I to III Ambulant cerebral palsy (Josenby et al 2012,38 Dudley et al 201337) Spasticity:

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